Abstract: To solve the problem of difficult settling of fine gangue in Shaqu coal preparation plant,analyzed the influences of size composition,pulp concentration and water hardness on the flocculating settlement of particles.The result shows that when finer size composition and increasing of pulp concentration it will worsen the sedimentation effect of fine gangue particles.The synergy of coagulant and flocculant can increase the settling rate of particles and reduce the turbidity of clarified liquor,and the desired settlement can be obtainable by batch addition of flocculant.Enhancing the hardness of water is helpful to improve the sedimentation effects of fine particles.